"""The three HTTP listeners: page (loopback, behind oauth2-proxy), internal API, metrics."""
import json
import logging
import threading
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from urllib.parse import urlsplit

import page
import trivy
from state import parse_ts

log = logging.getLogger("vuln-scanner.server")

MAX_TRIAGE_BYTES = 256 * 1024
MAX_REMEDIATION = 5000
REMEDIATION_STATES = ("pr-open", "approval-requested", "no-update-identified", "not-tracked")


class _Handler(BaseHTTPRequestHandler):
    server_version = "vuln-scanner"
    sys_version = ""
    timeout = 30
    engine = None

    def log_message(self, fmt, *args):  # request lines carry filters; keep them out of the log
        return

    def _send(self, status, headers, body):
        self.send_response(status)
        for name, value in headers.items():
            self.send_header(name, value)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def _text(self, status, body, content_type="text/plain; charset=utf-8"):
        self._send(status, {"Content-Type": content_type}, body.encode("utf-8"))


class _PageHandler(_Handler):
    def send_error(self, code, message=None, explain=None):  # keep the CSP on error responses too
        status, headers, body = page.not_found()
        self._send(code, headers, body)

    def do_GET(self):
        parts = urlsplit(self.path)
        if parts.path == "/":
            self._send(*self.engine.render_page(parts.query))
        elif parts.path == "/healthz":
            self._text(200, "ok\n")
        else:
            self._send(*page.not_found())


class _MetricsHandler(_Handler):
    def do_GET(self):
        path = urlsplit(self.path).path
        if path == "/metrics":
            self._text(200, self.engine.metrics_text(), "text/plain; version=0.0.4; charset=utf-8")
        elif path == "/healthz":
            healthy = self.engine.healthy()
            self._text(200 if healthy else 503, "ok\n" if healthy else "scan loop stopped\n")
        else:
            self._text(404, "not found\n")


class _InternalHandler(_Handler):
    def do_GET(self):
        path = urlsplit(self.path).path
        if path == "/report.json":
            body = self.engine.report_bytes()
            if body is None:
                self._text(503, "no report yet\n")
            else:
                self._send(200, {"Content-Type": "application/json"}, body)
        elif path == "/healthz":
            self._text(200, "ok\n")
        else:
            self._text(404, "not found\n")

    def do_POST(self):
        if urlsplit(self.path).path != "/triage":
            self._text(404, "not found\n")
            return
        content_type = (self.headers.get("Content-Type") or "").split(";", 1)[0].strip().lower()
        if content_type != "application/json":
            self._text(415, "content type must be application/json\n")
            return
        try:
            length = int(self.headers.get("Content-Length", ""))
        except ValueError:
            self._text(411, "a content length is required\n")
            return
        if length < 0 or length > MAX_TRIAGE_BYTES:
            self._text(413, "body too large\n")
            return
        raw = self.rfile.read(length)
        try:
            document = json.loads(raw)
        except ValueError:
            self._text(400, "body is not JSON\n")
            return
        errors = validate_triage(document)
        if errors:
            self._text(400, errors[0] + "\n")
            return
        self.engine.record_triage(document)
        self._send(204, {}, b"")


def validate_triage(document):
    """Error strings for a POST /triage body; empty means valid. Exact shape, nothing extra."""
    if not isinstance(document, dict) or set(document) != {"heartbeatAt", "remediation"}:
        return ["body must have exactly heartbeatAt and remediation"]
    if parse_ts(document["heartbeatAt"]) is None or len(document["heartbeatAt"]) > 64:
        return ["heartbeatAt must be RFC 3339"]
    entries = document["remediation"]
    if not isinstance(entries, list) or len(entries) > MAX_REMEDIATION:
        return ["remediation must be a list of at most " + str(MAX_REMEDIATION) + " entries"]
    for index, entry in enumerate(entries):
        prefix = "remediation[" + str(index) + "]: "
        if not isinstance(entry, dict) or set(entry) != {"image", "state", "url", "updatedAt"}:
            return [prefix + "must have exactly image, state, url, updatedAt"]
        if not isinstance(entry["image"], str) or not 0 < len(entry["image"]) <= 512:
            return [prefix + "image must be a string of at most 512 characters"]
        if entry["state"] not in REMEDIATION_STATES:
            return [prefix + "unknown state"]
        url = entry["url"]
        # safe_url is the same rule the report schema enforces, so a value accepted here cannot make
        # the report invalid. Empty is refused: safe_url returns "" for it, and the schema does not.
        if url is not None and (not isinstance(url, str) or not url or trivy.safe_url(url) != url):
            return [prefix + "url must be null or an http(s) URL"]
        if parse_ts(entry["updatedAt"]) is None or len(entry["updatedAt"]) > 64:
            return [prefix + "updatedAt must be RFC 3339"]
    return []


def serve(handler_type, address, engine):
    handler = type(handler_type.__name__, (handler_type,), {"engine": engine})
    server = ThreadingHTTPServer(address, handler)
    server.daemon_threads = True
    thread = threading.Thread(target=server.serve_forever, name="http-" + str(address[1]), daemon=True)
    thread.start()
    return server


def start_all(engine, page_address, internal_address, metrics_address):
    return [
        serve(_PageHandler, page_address, engine),
        serve(_InternalHandler, internal_address, engine),
        serve(_MetricsHandler, metrics_address, engine),
    ]